Antithamnionella ternifolia -

The area of origin of A. ternifolia is uncertain ^[2], although it is suspected that this red alga originates from the Southern Hemisphere ^{[3, 4]}. The situation is complex since many very similar species, and probably related species, occur in different parts of the world ^{[2, 5]}.

This non-indigenous red seaweed grows on a variety of substrates, ranging from algae and stones to artificial materials, such as pontoons and buoys. They can be found up to a depth of 25 metres in both sheltered and exposed environments ^[6].

First observation in Belgium

A. ternifolia was first observed in 1970, in the Sluice Dock of Ostend, under the name Antithamnion sarniensis ^[7], attached to a so-called ‘Japanese basket’ used for experiments related to the cultivation of oysters^[8].

Spreading in Belgium

In Belgium, A. ternifolia is often confused with Antithamnionella spirographidis. These two red algae are so similar that scientists are not entirely sure whether they are two different species. Since such red algae are hard to distinguish based on morphological characteristics, further research is needed to find out how many species occur along our coast ^[9]. A. spirographidis may also have been introduced into European waters ^[10].

Both red algae are found in the ‘Verbindingsdok’ and Baudouin Canal ^[11] in the inner Port of Zeebrugge, as well as on pontoons in the marina of Zeebrugge ^[12]. It is said that in the Sluice Dock of Ostend, a couple of algae are growing on Harvey's siphon weed Melanothamnus harveyi ^[4], another non-indigenous species.

Spreading in neighbouring countries

Although a few specimens of this species were found in Plymouth (Southwest Britain) as early as 1906 ^[6], although, under a different name (Antithamnionella cruciatum f. tenuissimum), this sighting wasn't the first observation in Europe. The observation from 1910, in Cherbourg-Octeville (Northwest France) ^[13], is usually considered the first European observation ^[2]. In the meantime, A. ternifolia has spread along the entire Atlantic Coast of Europe. It is found from Portugal to Denmark and is also present along the south and west coasts of Great Britain – as far as Argyll in western Scotland – and along the coast of Ireland ^{[6, 14, 15]}.

In the Netherlands, A. ternifolia was found for the first time in 1951 but has been observed only incidentally ^[2]. A. spirographidis has been common in the Dutch Eastern Scheldt since 1993 ^[2]. Furthermore, this species has been collected from the neighbouring Lake Grevelingen ^[2], and the entrance of the Sloehaven on the Western Scheldt ^[16].

In 2010, A. ternifolia was observed in the German part of the Wadden Sea near the island of Sylt, west of the German-Danish border ^[17].

Most likely, A. ternifolia got introduced to Europe via attachment to ship hulls and ropes. It is possible that the first introduction to Europe took place via Australian ships ^[3]. Also, some specimens got introduced through aquaculture, where the seaweed attached itself to oysters, transported to Europe for cultivation ^[16].

Rapid growth and vegetative reproduction through fragmentation – whereby broken off pieces can grow into a new individual – are the main explanations for the success of this non-native species ^[3]. A. ternifolia isn’t picky about the type of substrate and it grows on both natural (e.g. algae, shellfish or stones) and artificial substrates (e.g. pontoons and buoys) ^[6].

A. ternifolia, like A. spirographidis, has glandular cells containing certain toxic chemicals, such as eosin ^{[18, 19]}. It is believed that these substances serve as a defence mechanism against grazing by herbivores ^[2].

A. ternifolia covers large distances by attaching itself to the hulls of transport ships ^[3], while local recreational boats provide a rapid spread between different marinas ^[2]. This non-indigenous red seaweed tolerates a wide temperature gradient ^[3].

The species attaches itself to hard structures in harbours and on ships ^[3]. Biofouling on ships can have financial implications since biofouling communities increase resistance when sailing. The removal of these communities is very costly and can be avoided by using antifouling paints ^[20]. The effects of A. ternifolia on its natural environment are unknown.

A. ternifolia is bright red and forms woolly tufts of 1-2 centimetres. It closely resembles another non-indigenous species found in our region, namely A. spirographidis. These species can only microscopically be distinguished. The side branches of A. spirographidis are opposite, not planted in a ‘wreath’ on the lateral axes, as in A. ternifolia ^{[6, 21, 22]}.

A. ternifolia is found mainly from the low water line to a depth of 25 metres. Both sheltered and strongly exposed environments with strong currents belong to its habitat.

This species reproduces asexually, sexually and vegetatively. In Europe, A. ternifolia reproduces mainly by vegetative and asexual reproduction. Vegetative reproduction occurs by fragmentation, where each fragment can grow into a new individual. In asexual reproduction, spores give rise to new individual algae after dispersal ^{[6, 21]}.

[1]          World Register of Marine Species (WoRMS) (2020). Antithamnionella ternifolia (J.D.Hooker & Harvey) Lyle. [http://www.marinespecies.org/aphia.php?p=taxdetails&id=163275] (2020-11-17).

[2]          Maggs, C.A.; Stegenga, H. (1999). Red algal exotics on North Sea coasts. Helgol. Meeresunters. 52: 243-258. [http://www.vliz.be/en/imis?module=ref&refid=110857]

[3]          Eno, N.C.; Clark, R.A.; Sanderson, W.G. (Ed.) (1997). Non-native marine species in British waters: a review and directory. Joint Nature Conservation Committee: Peterborough. ISBN 1-86107-442-5. 152 pp. [http://www.vliz.be/nl/imis?module=ref&refid=24400]

[4]          Heytens, M.; De Clerck, O.; Coppejans, E. (2007). Studie van macrowiergemeenschappen van de Spuikom van Oostende in functie van de Kaderrichtlijn water. Universiteit Gent - Vakgroep Biologie - Afdeling Algologie: Gent. 65 pp. [http://www.vliz.be/en/imis?module=ref&refid=118621]

[5]          Athanasiadis, A. (1990). Evolutionary biogeography of the North Atlantic antithamnioid algae, in: Garbary, D.J. et al. Evolutionary biogeography of the marine algae of the North Atlantic. NATO ASI Series G: Ecological sciences, 22. Springer: Berlin: pp. [http://www.vliz.be/en/imis?module=ref&refid=211977]

[6]          Maggs, C.A.; Hommersand, M.H. (1993). Seaweeds of the British Isles: Volume 1 Rhodophyta. Part 3A Ceramiales. Seaweeds of the British Isles, 1. Natural History Museum: London. ISBN 1-898298-81-5. 444 pp. [http://www.vliz.be/en/imis?module=ref&refid=65109]

[7]          Otten, B.G.; Stegenga, H. (1995). Naamswijziging van roodwieren. Het Zeepaard 55: 108-111. [http://www.vliz.be/en/imis?module=ref&refid=206914]

[8]          Leloup, E. (1973). Recherches sur l'ostréiculture dans le bassin de chasse d'Ostende en 1970 et 1971. Bull. Kon. Belg. Inst. Natuurwet. Biologie 49(10): 1-23. [http://www.vliz.be/en/imis?module=ref&refid=3473]

[9]          De Clerck, O. (2011). Persoonlijke mededeling

[10]        Athanasiadis, A. (1996). Morphology and classification of the Ceramioideae (Rhodophyta) based on phylogenetic principles. Opera Botanica, 128. Council for Nordic publications in Botany: Copenhagen. ISBN 9788788702194. 216 pp. [http://www.vliz.be/nl/catalogus?module=ref&refid=312305]

[11]        Dumoulin, E. (2011). Persoonlijke mededeling

[12]        De Blauwe, H.; Dumoulin, E. (2009). De zeefauna en -flora uit de jachthaven van Zeebrugge, in het bijzonder de fouling-organismen van drijvende pontons. De Strandvlo 29(2): 41-63. [http://www.vliz.be/imis/imis.php?module=ref&refid=139489]

[13]        Westbrook, M.A. (1930). Notes on the distribution of certain marine red algea. J. Bot. 68: 257-264. [http://www.vliz.be/en/imis?module=ref&refid=140612]

[14]        Lyle, L. (1922). Antithamnionella, a new genus of algae. J. Bot. 60: 346-350. [http://www.vliz.be/imis?module=ref&refid=98395]

[15]        ICES Advisory Committee on the Marine Environment (2006). Report of the Working Group on Introductions and Transfers of Marine Organisms (WGITMO) 16-17 March 2006 Oostende, Belgium. CM Documents - ICES. CM 2006(ACME:05). ICES: Copenhagen. 330 pp. [http://www.vliz.be/en/imis?module=ref&refid=111237]

[16]        Wolff, W.J. (2005). Non-indigenous marine and estuarine species in the Netherlands. Zool. Meded. 79(1): 3-116. [http://www.vliz.be/en/imis?module=ref&refid=101200]

[17]        Buschbaum, C.; Lackschewitz, D.; Reise, K. (2012). Nonnative macrobenthos in the Wadden sea ecosystem. Ocean Coast. Manag. 68: 89-101. [http://www.vliz.be/nl/catalogus?module=ref&refid=301901]

[18]        Fenical, W. (1975). Halogenation in the Rhodophyta: a review. J. Phycol. 11: 245-259. [http://www.vliz.be/en/imis?module=ref&refid=140614]

[19]        Hay, M.E.; Fenical, W. (1988). Marine plant-herbivore interactions: the ecology of chemical defence. Annu. Rev. Ecol. Syst. 19: 111-145. [http://www.vliz.be/en/imis?module=ref&refid=142263]

[20]        Schultz, M.P.; Bendick, J.A.; Holm, E.R.; Hertel, W.M. (2010). Economic impact of biofouling on a naval surface ship. Biofouling 27(1): 87-98. [http://www.vliz.be/en/imis?module=ref&refid=206434]

[21]        Coppejans, E. (1998). Flora van de Noord-Franse en Belgische zeewieren. Scripta Botanica Belgica, 17. Nationale Plantentuin van België: Meise. ISBN 90-72619-41-2. 462 pp. [http://www.vliz.be/en/imis?module=ref&refid=4963]

[22]        Verlaque, M.; Ruitton, S.; Mineur, F.; Boudouresque, C.F. (2015). CIESM atlas of exotic species in the Mediterranean: 4. Macrophytes. CIESM Publishers: Monaco. ISBN 9789299000342. 364 pp. [https://www.vliz.be/nl/catalogus?module=ref&refid=332273]

VLIZ Alien Species Consortium (2020). Antithamnionella ternifolia. Non-native species of the Belgian part of the North Sea and bordering estuaries anno 2020. Flemish Institute for the Sea (VLIZ). 5 pp.